This invention relates to electrosurgery and more particularly to electrosurgical electrodes (e.g., probes, blades, forceps and the like) for use in performing electrosurgery. As is known to those skilled in the art, modern surgical techniques typically employ radio frequency (RF) cautery to cut tissue and coagulate the same to stop bleeding encountered in performing surgical procedures. For historical perspective and details of such techniques, reference is made to U.S. Pat. No. 4,936,842.
As is known to those skilled in the medical arts, electrosurgery is widely used and offers many advantages including that of the use of a single surgical tool for both cutting and coagulation. A variety of proposals have heretofore been embodied in existing electrosurgical implements. Examples of such proposals include those set forth in U.S. Pat. No. 4,534,347 granted to Leonard S. Taylor Aug. 13, 1985, U.S. Pat. No. 4,674,498 granted to Peter Stasz Jun. 23, 1987, and U.S. Pat. No. 4,785,807 granted to G. Marsden Blanch on Nov. 22, 1988.
The Taylor patent discloses an implement having a sharpened exposed edge (e.g., knife-blade like geometry) which is employed to perform conventional mechanical cutting of tissue while the blade is configured to act as a microwave radiator to transfer microwave energy by radiation into adjacent tissue to effect desired cauterization.
The Stasz patent sets forth several embodiments which disclose partly coated, partly exposed blades adapted for three modes of operation. These three modes are said to be: (1) a standard surgical cutting blade with a sharp edge when no electrical power is applied to it; (2) an electrocautery blade when a high voltage is applied between conductive surfaces of the blades sufficient to create a discharge arc therebetween for cutting and cauterizing of tissue; and (3) a low voltage cautery tool where I.sup.2 R losses create heat to cauterize tissue.
The Blanch patent discloses an unsharpened blade which has been entirely coated with an insulating layer so that cutting is performed by electrical energy capacitively transferred through the insulating layer to the tissue which is to be cut rather than by conventional mechanical action. In such electrosurgery, "cutting" is accomplished when energy transfer is sufficient to cause water in tissue cells to boil, thus rupturing the cell membranes by internal rather than external forces. Relatively high energy levels have been required to effect such electrosurgical cutting
While the Blanch proposals have constituted an important advance in the art and have found wide-spread acceptance in the field of electrosurgery, there has been a continuing need for further improvement in electrosurgery to effect in a relatively simple geometric configuration, a reduction in thermal necrosis thereby decreasing post-operative complication, reducing eschar production, reducing incidence of heat damage to tissue away from the cutting site, and increasing the speed of cutting.